1. Field of the Invention
The present invention relates to a system for anchoring a reinforcement member or rock bolt in the hole of a rock formation or a structural body. More specifically, the present invention is directed to a novel two-component filler-containing rock bolt anchoring system. The present invention also relates to a method of preparing and method of using the rock bolting anchoring system.
2. Description of the Related Art
Reactive systems for anchoring reinforcing members in holes in rock formations or structural bodies are commonly used in various industries. For example, in the mining industry, reactive systems are used to secure bolts used in mine roofs to prevent collapse thereof.
Such systems typically include two components. The first component is a hardenable synthetic resin formulation, and the second component is a cross-linking catalyst formulation. Prior to use, the two components are kept isolated from one another. Upon mixing of the first and second components, the catalyst initiates a cross-linking reaction in the synthetic resin formulation, resulting in a hardened or cured resin. U.S. Pat. Nos. 4,260,699, 4,273,689, 4,280,943, 4,518,283 and 4,616,050 disclose various two-component systems, the contents of which are hereby incorporated by reference.
In two-component systems, the resin and the catalyst formulations can be held in separate compartments in a single container, commonly referred to as a capsule, a sausage, a cartridge, or an ampule. The two formulations are separated, for example, by one or more plastic walls or a plastic film. The capsule is inserted into a hole in the rock formation or body in which the bolt is to be secured. The bolt is then inserted through the capsule to the back of the hole and is then spun. The wall or walls separating the compartments are thereby broken, causing the resin formulation and the catalyst formulation to mix together and react, thereby hardening around the bolt. After being spun, the bolt is held in place by applying a force against the bolt until the resin is set.
The acceptance of a two-component rock bolt anchoring system is dependent upon numerous properties measured by those skilled in the art. Such properties include displacement, yield point, stall, cycle time and permanent displacement. Tests for many of those properties are known in the art. For example, various tests are provided in the MSHA Standard Block Test, the contents of which are hereby incorporated by reference.
A hardenable synthetic resin composition that has gained wide acceptance as a component of rock bolt anchoring systems is a composition containing an unsaturated polymerizable polyester resin and a monomeric polymerizable ethylenic cross-linking agent therefor. These materials, together with a polymerization inhibitor or stabilizer, and a promoter for a peroxide catalyst, constitute a first part of the system or the resin component. A peroxide catalyst system for initiating the crosslinking polymerization is contained in a second part of the system or the catalyst component. The catalyst component is kept separated from the resin component until the hardening reaction is to take place. When the two components are combined and mixed, the action of the catalyst causes the cross-linking reaction between the polyester and ethylenic monomer to take place, resulting in a thermoset, hard resin.
Particulate inert fillers or aggregates are nearly always added to the resin component of anchoring systems. Fillers have been reported (e.g., in U.S. Pat. No. 3,731,791) to reduce the shrinkage of the resinous mass which occurs during polymerization, and they also reduce the cost of the product because they replace a portion of the more-expensive resin composition. A variety of materials have been disclosed as fillers. See, e.g., U.S. Pat. No. 4,280,943, the disclosure of which is incorporated herein by reference. Therein, it is disclosed that, in order to ensure filler loadings in the 70-80 percent range while retaining adequate fluidity in resin-based compositions, the filler particle size distribution should be from 150 mesh to 300 mesh (0.05 mm to 0.1 mm).
As a result of the desire to reduce cost, the use of fillers in high concentrations has become very desirable over the years. However, as filler loading is pushed to higher levels, the flowability and dispersibility characteristics of the compositions decrease. Further, the strength of the final product weakens to the point that the resinous systems can no longer be utilized in securing or anchoring rock bolts.
In order to ameliorate the aforementioned problem, U.S. Pat. No. 4,616,050 describes a highly filled resin composition said to have improved flowability and dispersibility characteristics, and improved strength. Therein it is disclosed to employ a filler in the resinous component and, optionally, in the catalyst component which includes coarse particles.
The coarse filler comprises particles in a size range whose minimum is about 1 mm, and whose maximum is about 12.5 mm. The remainder of filler includes a fine filler component comprised of particles whose maximum size is below 1 mm. The presence of the coarse filler component in the composition results in a workable viscosity at high total filler concentrations and better dispersibility, requiring less strenuous mixing conditions when the resin composition is to be blended with a catalyst. The presence of larger amounts of filler in the resin component, and in the total product, is said not to deleteriously affect the presetting workability of the product (e.g., ease of bolt insertion and rotation therein in bolt-anchoring), and the anchorage strength of hardened grouts is improved.
While the above systems are known in the art, there remains a need in the art for additional means for providing highly filled systems while improving the flowability, dispersibility and strength characteristics.